1. Field of the Invention
The present invention relates to dynamic fluid/gel zones for contact lenses, and more particularly to contact lenses incorporating one or more dynamic fluid/gel zones that may be utilized for one or both of delivering one or more therapeutic, nutritional or pharmacological agents, and dynamic, cosmetic eye enhancement.
2. Discussion of the Related Art
Myopia or nearsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point before they reach the retina. Myopia generally occurs because the eyeball or globe is too long or the cornea is too steep. A minus powered spherical lens may be utilized to correct myopia. Hyperopia or farsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point after they reach or behind the retina. Hyperopia generally occurs because the eyeball or globe is too short or the cornea is too flat. A plus powered spherical lens may be utilized to correct hyperopia. Astigmatism is an optical or refractive defect in which an individual's vision is blurred due to the inability of the eye to focus a point object into a focused image on the retina. Unlike myopia and/or hyperopia, astigmatism has nothing do to with globe size or cornea steepness, but rather it is caused by an abnormal curvature of the cornea. A perfect cornea is spherical whereas in an individual with astigmatism, the cornea is not spherical. In other words, the cornea is actually more curved or steeper in one direction than another, thereby causing an image to be stretched out rather than focused to a point. A cylindrical lens rather than a spherical lens may be utilized to resolve astigmatism.
A toric lens is an optical element having two different powers in two orientations that are perpendicular to one another. Essentially, a toric lens has one power, spherical, for correcting myopia or hyperopia and one power, cylinder, for correcting astigmatism built into a single lens. These powers are created with curvatures at different angles which are preferably maintained relative to the eye. Toric lenses may be utilized in eyeglasses, intraocular lenses and contact lenses. The toric lenses used in eyeglasses and intraocular lenses are held fixed relative to the eye thereby always providing optimal vision correction. However, toric contact lenses may tend to rotate on the eye thereby temporarily providing sub-optimal vision correction. Accordingly, toric contact lenses also include a mechanism to keep the contact lens relatively stable on the eye when the wearer blinks or looks around.
In order to treat infection, inflammation, glaucoma, and other ocular diseases, drugs are often required to be administered to the eye. A conventional method of drug delivery is by topical application to the eye's surface. The eye is uniquely suited to this surface route of drug administration because, properly constituted, drugs can penetrate through the cornea, rise to therapeutic concentration levels inside the eye, and exert their beneficial effects. In practice, eye drops currently account for more than ninety-five (95) percent of drug delivery methods for the eye. Rarely are drugs for the eye administered orally or by injection, either because they reach the eye in too low a concentration to have the desired pharmacological effect, or because their use is complicated by significant systemic side effects.
Eye drops, though effective, are unrefined and inefficient. When an eye drop is instilled in the eye, it typically overfills the conjuctival sac, the pocket between the eye and the eyelids, causing a substantial portion of the drop to be lost due to overflow of the eyelid margin onto the cheek. In addition, a substantial portion of the drop remaining on the ocular surface is washed away by tears into the tear drainage system, thereby diluting the concentration of the drug. Not only is this share of the drug dose lost before it can cross the cornea, but this excess drug may be carried into the nose and throat where it is absorbed into the general circulation, sometimes leading to serious systemic side effects. The small portion of the drug in the eye drop which does penetrate the cornea results in an initial peak tissue concentration, a higher level than is required for the initial pharmacological effect. This tissue concentration then gradually decreases, such that by the time the next eye drop is due, the tissue concentration and the intended pharmacological effect may be too low.
To compound the problems described above, patients often do not use their eye drops as prescribed. Often, this poor compliance is due to an initial stinging or burning sensation caused by the eye drop. Certainly, instilling eye drops in one's own eye can be difficult, in part because of the normal reflex to protect the eye. Older patients may have additional problems instilling drops due to arthritis, unsteadiness, and decreased vision, and pediatric and psychiatric patient populations pose difficulties as well. Accordingly, contact lenses may provide a viable means for solving the problems of reliable and efficient drug delivery to the eye.
The use of tinted or colored contact lenses to alter or enhance the natural color of the iris is well known. In manufacturing conventional tinted contact lenses, it is known to use either or both translucent and opaque colors in one layers of color with the object of creating a natural appearing tinted iris. Typically, the color layers are each applied at a single thickness. This provides color variation only with the use of multiple colors or points at which the translucent color overlaps another color layer. However, the natural iris is composed of a large number of different colors and color combinations intermixed to create color variations. The relatively small number of colors and color layers that may be utilized in producing tinted contact lenses limits the designer's ability to create a natural appearing lens. Accordingly, it would be advantageous to create a form of dynamic eye color enhancement above simply altering the color of the iris.
Accordingly, it would be advantageous to design a contact lens with dynamic stabilization zones that auto-position the contact lens quickly and hold and/or maintain the desired position for optimal visual acuity regardless of eye movement, blinking and tears. It would also be advantageous to design a contact lens to deliver one or more therapeutic, nutritional or pharmacological agents to the eye. It would also be advantageous to provide dynamic, cosmetic eye enhancement utilizing contact lenses.